The present invention relates to a separating agent for solid-phase extraction; a column or cartridge for solid-phase extraction using the separating agent; a method for concentrating a subject to be separated; a method for removing impurities; a method for solid-phase extraction of an environmental, medicinal and/or biological samples; and a method for pre-treating a protein component-containing sample. These methods make use of the column or cartridge packed with the separating agent.
The solid-phase extraction method means a physical extraction process in which a liquid and a solid are concerned. In the solid-phase extraction technique, when the affinity of a substance to be separated for a solid phase is, for instance, greater than that of the substance to be separated for the solvent in which the substance is dissolved (sample solution) and when the sample solution passes through the solid phase bed, the substance is concentrated on the surface of the solid phase, while other components present in the sample solution pass through the solid phase bed. Thus, the target substance can be separated. Contrary to the foregoing method, there has been known a method in which the target substance can pass through a solid phase bed, while other components of the sample solution are fixed onto the solid phase to thus separate the same. As separating agents used in the solid-phase extraction technique, there have been known, for instance, inorganic base materials such as silica gel or chemically modified silica gel obtained by chemically modifying the surface of silica gel particles; and organic base materials such as synthetic polymer type ones represented by styrene-divinyl benzene copolymers and those obtained by chemically modifying the surface of these organic base materials.
In general, the synthetic polymeric base material used in the chromatography technique is constituted by a large number of discrete particles having a large number of fine pores of a small depth distributed on the surface thereof and having a regular shape, preferably a spherical shape.
In most of cases, the synthetic polymeric base material is prepared according to the suspension polymerization technique since this technique is quite simple to handle and it is excellent in the reproducibility. In general, the resulting polymer particles are subjected to an appropriate classification treatment to thus obtain only a product having a particle size favorably used as a material which is packed into a column for chromatography (packing material) (see, for instance, Patent Documents Nos. 1 to 11 and Non-Patent Document 1 listed below):    Patent Documents No. 1: JP-A-2002-139482    Patent Documents No. 2: JP-A-2001-343378    Patent Documents No. 3: JP-A-Hei 6-258203    Patent Documents No. 4: JP-A-2000-514704    Patent Documents No. 5: JP-A-2002-517574    Patent Documents No. 6: JP-A-Hei 5-302917    Patent Documents No. 7: WO01/059444    Patent Documents No. 8: Japanese Patent No. 3,055,911    Patent Documents No. 9: JP-A-2000-26551    Patent Documents No. 10: JP-A-Hei 8-325428    Patent Documents No. 11: U.S. Pat. No. 4,140,653B    Non-Patent Document 1: KUNIO FURUSAWA et al., “Syntheses of Composite Polystyrene Latices with Silica Particles in the Core”, Journal of Colloid and Interface Science, 1986, Vol. 109, No. 1.